Stoqn Tochev asked about securely erasing sensitive files without destroying everything on his hard drive. I'll discuss SSDs, as well.
When you delete a file conventionally, it goes into the Recycle Bin, where it can be easily restored. When you empty the Recycle Bin, Windows makes the space where the file once resided available for other files. But the data from the file remains until another file writes over it.
Things have changed since I last covered this topic in 2013. SSDs have become more popular, and they work differently. Also, as Windows 8 has gotten older and more mature, I felt I should discuss a tool built into that operating system. Finally, I've replaced one free tool I used to recommend with another, easier offering.
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You can securely erase (or wipe) a hard drive's data by writing ones and zeros over it (I'll get to SSDs below). There are three approaches to the job:
- You can wipe the entire drive or partition. This is theoretically the most secure approach, but it's slow, difficult, and dangerous. Wiping the C: partition will destroy your Windows installation, and wiping the entire drive may make a Windows reinstall impossible.
- You can wipe individual files that contain sensitive information. This is simple and relatively quick. If you know what needs to be destroyed, this is the best way.
- You can also wipe the free space that's available for new files. After all, that's where the security problem resides.
Here are three programs I recommend for this job:
Ccleaner: Amongst its many other capabilities, this free, all-around cleanup tool can wipe partitions or free space. Go to Tools > Drive Wiper and make your choices. The Entire Drive option won't let you wipe C:, but it will let you wipe a separate data partition.
File Shredder: This small, light, free program does exactly what the name says. It integrates with Windows Explorer, so you can right-click a file and wipe it off the drive. It also wipes (or, if you prefer, shreds) free space.
Windows 8(.1) Recovery Environment: This tool, built into Windows 8, allows you to reinstall Windows. When you go through the install wizard, you'll find an option to erase data "thoroughly." That means a wipe.
The difference with SSDs
Now then, about SSDs: Wiping is all about massive writing to the drive, and as I've explained, that's not a good idea with flash memory. Besides, SSDs store files in an entirely different way than magnetic media, and wiping just won't work.
Fortunately, most SSDs have the ability to do a drive-wide secure erase. Go to the drive manufacturer's website for specific instructions. You'll probably have to download a program specific to that company. You can also just search on the manufacturer's name and this phrase:
ssd secure erase utility.
One more piece of advice: If you keep your sensitive files properly encrypted, wipes are arguably unnecessary.